Based on the analysis of winter field survey and thermal environment measurement, the buffer-space design can obviously improve indoor thermal environment in the residential buildings of Lhasa. However, the indoor winter thermal environment of non-heating rooms still need to be improved. Local people have strong heating demand for residential buildings. All the clues lead to the fast growing tendency of heating energy consumption and environmental load in Lhasa. The basic simulation models for understanding the buffer-space's effect to heating energy consumption are established from the common residential buildings in Lhasa, and the factors include south and north buffer-space's depth design. Result shows that buffer-space can obviously reduce winter heating energy consumption. Along with the south buffer-space's depth increasing, the heating energy consumption shows the tendency of continuous increasing; as for the north buffer-space, the tendency is firstly getting decreasing and then increasing, and the energy consumption among models is not large. The heating energy consumption comparison study between common model and optimal buffer-space design model shows that buffer-space design can obviously reduce the heating energy consumption.